Lucky For Us: Horseshoe Crabs

HOMELY CRITTERS’ BLUE BLOOD PLAYS KEY ROLE IN DRUG TESTING

Hartford Courant, July 21, 2008

By DAVID FUNKHOUSER

WESTPORTAt the west end of Southport Beach, Doug Grabe hauled a folding table and plastic buckets from his truck and set up on the sand for a couple hours of counting, measuring and tagging horseshoe crabs.
Grabe’s unwitting subjects already were starting to arrive, dozens of them crawling and nudging their way from Long Island Sound up the mouth of Sasco Creek. Their movement was timed to a new moon high tide that flooded the creek’s grassy banks and gravelly bottom and pushed the water up onto the sand.
Horseshoe crabs have been around for 300 million years – older than the dinosaurs. As cumbersome and as homely as they appear in their tank-like brown shells, their light blue blood supplies an ingredient indispensable to human health.


May and June are spawning season, and at high tides along the Eastern Seaboard from Maine to Florida, hundreds of thousands of horseshoe crabs – Limulus polyphemus – repeat the ritual, searching for good spots to lay their eggs.
Grabe, a marketing entrepreneur from Fairfield, is one of hundreds of volunteers helping researchers learn about horseshoe crabs. On this day, the volunteers included his son and 14 other second-graders from The Unquowa School in Fairfield, who arrived soon after him. As the children spilled onto the beach, Grabe explained their task, and the youngsters began to gingerly gather specimens.
Though they look well-armored, the crabs do not bite, and their pointed tails and pincerlike legs are harmless. The ancient creatures – not really crabs; more closely related to spiders and scorpions – have come under close study only in the past decade, because of fears that over-harvesting and loss of habitat might already have led to population declines.

TAGGING, TRACKING
At the folding table, researcher Jennifer H. Mattei set down her clipboard, tally sheets and a box of white plastic disks, each with an ID number and a phone number to call for anyone who finds a tagged crab. The tags help scientists learn how far the crabs roam. More than 80,000 of them have been tagged this way along the Atlantic Coast, according to the Atlantic States Marine Fisheries Commission. About 10 percent have been recaptured and reported.
Mattei is chairwoman of the biology department at Sacred Heart University and the head of Project Limulus, a collaboration of many groups that has two goals: to study the crabs and their predators; and to get children outdoors to learn about nature.
Alex Morse, 8, lifted a pair of out of the water and brought them up the beach to Mattei. A male crab was using his stumpy foreclaws to cling to the back of the much larger female’s shell. Males ride along in this way as the females plow into the sand, and after the female lays her thousands of eggs, he’ll deposit his sperm onto them.
Mattei measured the female: 26 centimeters across her widest spot. Mattei pointed out two compound eyes tucked into ridges along the top of the shell. Research on those eyes has revealed important information about the functioning of human eyes, and earned three researchers the 1967 Nobel Prize in medicine.
Mattei punched a small hole along the edge of the female’s shell, and Alex snapped a plastic tag into place: No. 134928. After the male was measured and tagged (21.5 centimeters, No. 134941), the boy carried both back to the water and tried to encourage the male to get back on board.
Mattei stood cradling another large female in her arms, ignoring the wriggling legs and the long tail flapping up and down. She happily rattled off details of the crabs’ life: They cruise the bottom, eating worms and baby clams and oysters. Leather-like flaps cover their gills, allowing them to stay out of the water for hours, until another high tide comes along.
They molt until they are 10 or 12 years old, then are ready to breed. No one knows exactly how long they can live, but Mattei estimated 25 to 30 years. They also serve as a home to many other animals that attach to their shells – mussels, barnacles, slipper shells.

A VITAL TEST
Most intriguing, however, is the crab’s blood: It’s blue because it contains copper rather than hemoglobin, as in humans. It’s also the basis of a multimillion-dollar industry.
Horseshoe crab blood carries a clotting agent that can isolate bacterial toxins – and the federal Food and Drug Administration requires that it be used to test all intravenous drugs and vaccines for safety.
The test, using a compound called Limulus amoebocyte lysate, or LAL, also is standard for screening heart valves, hip replacements, breast implants and other prosthetic devices.
Fishermen last year brought half a million crabs to several companies on the East Coast that bleed them and process the precious compound. Some of those crabs ended up as bait, but most were released alive back to the sea. About 10 percent of the crabs do not survive the process.
Fishermen might get a couple dollars for a crab. But the lysate formula sells for about $15,000 to $17,000 a freeze-dried liter, according to Bill Hall, a marine specialist with the Delaware Sea Grant program who has spent years studying the crabs.
“The value to the pharmaceutical industry is in the billions,” Hall said, because the tests are so good at weeding out contaminated drugs. “It’s the best test around.”
Researchers are exploring other medical uses for the blood. One extract is being tested as a way to diagnose invasive fungal infections, especially helpful for transplant patients and others with suppressed immune systems.

USED FOR BAIT
As valuable as its blood might be, most of the crab catch continues to be used as bait for eel and conch.
More than 810,000 crabs were caught for bait last year, with the largest hauls in the waters off New York, Maryland and Massachusetts. Connecticut fishermen landed nearly 25,000 crabs last year, primarily for bait.
The largest crab concentration on the East Coast is around Delaware Bay, with the mid-Atlantic population estimated to be in the millions.
The population seemed to be declining in recent years, though “there are no signs of the horseshoe crab population crashing,” said Brad Spears, chairman of the Atlantic States Marine Fisheries Commission.
Fishing quotas instituted a decade ago have started to pay off, he said, and the population around Delaware Bay is now growing.
Penny Howell, a fisheries biologist with the Connecticut Department of Environmental Protection, signed on with Project Limulus and went out several nights this spring at high tide in search of spawning crabs. She is pretty sure the state’s population has shrunk.
“I grew up in Clinton and saw lots of crabs growing up,” she said.
“There used to be a lot of crabs, and now there aren’t.” She says one factor is certainly the loss of habitat because of development and more people using the beach.
The work that she and dozens of other volunteers are doing on 10 of the state’s beaches should help researchers fill in the blanks.

For more on Project Limulus: http://www.sacredheart.edu/pages/1 3692_project_limulus.cfm and http://www.horseshoecrab.org/index.html.

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